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  • cz 550 action threads

    what in the world is a m28x2sp3 thread? I want to build a 338 lapua rifle the action looks good but not familar with the thread.

  • #2
    Sounds like one of them wild metric jobs to me. "m28" is the diameter, "x2" is the Metric pitch, and I would suspect that "sp3" refers to the "Class" of fit. And I also suspect that it is very close to the Mauser 1.10" x 12 tpi. If you already know that this is the proper thread and you have access to a lathe that can cut Metric threads, what is the problem?

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    • #3
      HOLLY SMOKE!
      That's big bucks for just the action. FFL required too.

      http://www.brownells.com/aspx/ns/sto...=CZ+550+ACTION

      M28x2 is 28mm major diameter with a thread pitch of 2mm. The sp3 doesn't fit any spec I have. It may be similar to the H and D tolerances for threads.

      Ops, Al beat me to it.

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      • #4
        http://www.newyorktwistdrill.com/tap...l_data_02.html
        If you check the URL above the chart shows
        the differences between the 28x2 and the
        28x3. I wonder if they possibly use one or the other on these barrels. Just a thought.

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        • #5
          It wasn't a problem so much as to finding out what set my lathe gear box too.the sp3 is what was throwing me off.It also helped finding my lathes owners manual it had a metric conversion table in it and that is a 12tpi thread.

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          • #6
            Use the same measurements you would use if you were fitting a Douglas barrel blank to a Large ring '98 Mauser action.

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